Dampers are widely used in various industrial and commercial heating, ventilating and air conditioning (HVAC) systems. Single and multiple-blade dampers in particular are used to control airflow rates in a premises, prevent backflow and restrict smoke dispersion in fire safety applications, amongst other uses.
These dampers typically comprise an outer frame sized to either fit into a specified opening or to cover a specific opening, in various environments. For example, FIG. 1 illustrates a damper mounted to or on the wall of a plenum or HVAC unit 4; FIG. 2 illustrates a damper mounted to a duct 6 or in series with a duct 6; and FIG. 3 illustrates a damper mounted to the outlet of a blower 8. In each of these environments the damper controls airflow because the damper blades are movable from an open position in which air is permitted to flow through the airflow region bounded by the interior of the damper frame, and a closed position blocking the flow of air through the damper.
In many applications it is advantageous to securely close the damper blades so as to provide a substantially air-tight seal, for example in insulated dampers to prevent loss of heat and in backflow dampers to prevent potentially noxious gases from flowing into a premises or other habitable space. Conventional dampers thus provide damper stops extending into the interior airflow area in the path of the movement of the outer damper blades. This stops the damper blades at precisely the closed position and provides a surface against which the outer damper blades abut in order to inhibit airflow between the closed damper blades and the frame.
It is also important that the frame of a damper be structurally sound so as to retain its shape with fairly precise tolerances, otherwise leakage of air through the damper could occur. In the applications described above this is more than a mere inefficiency, and can result in loss of temperature control within a premises, or hazardous levels of noxious gases. The frame is thus constructed so to have structural integrity independent of the structure in which it is located, to prevent deformation that might cause leaks. Thus, in a prior art multiple-blade damper, as shown in FIG. 4, the frame is constructed from a fairly thick gauge of metal and is provided with 90 degree flanges which impart transverses rigidity to the sides and ends of the frame.
In such conventional dampers, blade stops are formed as separate pieces, typically extrusions, and affixed to the interior of the frame at the blade stop position by, for example, spot welding or fasteners. However, since the volume and flow rate of air flowing through the damper is in part determined by the area bounded by the interior of the frame, any structure extending into this area impedes airflow, not only by reducing the effective area within the frame but also by producing eddies and currents around the impinging structure that disrupt a laminar airflow pattern and cause additional resistance to the flow of air through the damper.
It would accordingly be advantageous to provide a single or multiple-blade damper comprising blade stops which do not impinge into the airflow area within the frame. It would further be advantageous to provide a damper comprising blade stops which assist in imparting structural integrity to the frame.
It will be appreciated that such dampers can be mounted into a structure or onto a structure for the selective control of airflow. References in the description to a damper mounted to a structure include all methods and means of fixing, securing and/or mounting a damper into a structure or onto a structure, and the invention is not in any way limited by the manner in which the damper is mounted to the structure.